Control voltages for power switchgear

Standards for control voltages for closing and tripping power circuit breakers were established by the National Electric Manufacturers Association (NEMA) and the American Standards Association (now the American National Standards Institute) many years ago. Subsequently these requirements were extended to other switchgear equipment such as motor operated disconnecting switches and capacitor switches. A working group (See Appendix I) under the auspices of the ANSI C37 committee has reviewed these requirements in light of modern technology, and has made certain recommendations for changes. The reasoning behind these proposed changes and some points of dissension voiced by both manufacturers and users are discussed.